Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof;

FIG. 5 is the fifth image thereof; and,

FIG. 6 is the sixth image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-6. The process or period in which one image transitions to another image forms no part of the claimed design. The broken lines around the figures show a display screen and form no part of the claimed design. The broken lines within the figures showing the text and the symbol form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 